In many industrial processes, workpieces, for example wafers, are etched to change the form of the workpiece in some manner. For example, during wafer processing and manufacture wafers, e.g., semiconductor wafers may be etched, for example with the goal to level the wafer, i.e., reduce a total thickness variation (TTV) of the wafer. To give an example, in some cases the wafer thickness influences electrical properties of semiconductor devices formed on the wafer, and therefore a small thickness variation is desirable to reduce variations of the electrical properties of manufactured semiconductor devices. For example, it is expected that in the future thickness variations of ±1 μm will be demanded for 8 inch wafers or even larger wafers.
To level the wafer, etching processes like spin etch processes where an etchant is dispensed on a rotating wafer, are used. For such and other etching processes, it is desirable to locally control the etching rate.